.\"	$OpenBSD: ftw.3,v 1.4 2003/10/30 18:52:58 jmc Exp $
.\"
.\" Copyright (c) 2003 Todd C. Miller <Todd.Miller@courtesan.com>
.\"
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.\" Sponsored in part by the Defense Advanced Research Projects
.\" Agency (DARPA) and Air Force Research Laboratory, Air Force
.\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
.\"
.Dd May 20, 2003
.Dt FTW 3
.Os
.Sh NAME
.Nm ftw, nftw
.Nd traverse (walk) a file tree
.Sh SYNOPSIS
.Fd #include <ftw.h>
.Ft int
.Fo ftw
.Fa "const char *path"
.Fa "int (*fn)(const\ char\ *, const\ struct\ stat\ *ptr, int\ flag)"
.Fa "int depth"
.Fc
.Ft int
.Fo nftw
.Fa "const char *path"
.Fa "int (*fn)(const\ char\ *, const\ struct\ stat\ *ptr, \
     int\ flag, struct\ FTW\ *)"
.Fa "int depth"
.Fa "int flags"
.Fc
.Sh DESCRIPTION
.Bf -symbolic
These functions are provided for compatibility with legacy code.
New code should use the
.Xr fts 3
functions.
.Ef
.Pp
The
.Fn ftw
and
.Fn nftw
functions traverse (walk) the directory hierarchy rooted in
.Fa path .
For each object in the hierarchy, these functions call the function
pointed to by
.Fa fn .
The
.Fn ftw
function passes this function a pointer to a NUL-terminated string containing
the name of the object, a pointer to a stat structure corresponding to the
object, and an integer flag.
The
.Fn nftw
function passes the aforementioned arguments plus a pointer to a
.Dv FTW
structure as defined by
.Aq Pa ftw.h
(shown below):
.Bd -literal
struct FTW {
    int base;	/* offset of basename into pathname */
    int level;	/* directory depth relative to starting point */
};
.Ed
.Pp
Possible values for the flag passed to
.Fa fn
are:
.Bl -tag -width FTW_DNR
.It Dv FTW_F
A regular file.
.It Dv FTW_D
A directory being visited in pre-order.
.It Dv FTW_DNR
A directory which cannot be read.
The directory will not be descended into.
.It Dv FTW_DP
A directory being visited in post-order
.No ( Ns Fn nftw
only).
.It Dv FTW_NS
A file for which no
.Xr stat 2
information was available.
The contents of the stat structure are undefined.
.It Dv FTW_SL
A symbolic link.
.It Dv FTW_SLN
A symbolic link with a non-existent target
.No ( Ns Fn nftw
only).
.El
.Pp
The
.Fn ftw
function traverses the tree in pre-order.
That is, it processes the directory before the directory's contents.
.Pp
The
.Fa depth
argument specifies the maximum number of file descriptors
to keep open while traversing the tree.
It has no effect in this implementation.
.Pp
The
.Fn nftw
function has an additional
.Fa flags
argument with the following possible values:
.Bl -tag -width FTW_MOUNT
.It Dv FTW_PHYS
Physical walk, don't follow symbolic links.
.It Dv FTW_MOUNT
The walk will not cross a mount point.
.It FTW_DEPTH
Process directories in post-order.
Contents of a directory are visited before the directory itself.
By default,
.Fn nftw
traverses the tree in pre-order.
.It FTW_CHDIR
Change to a directory before reading it.
By default,
.Fn nftw
will change its starting directory.
The current working directory will be restored to its original value before
.Fn nftw
returns.
.El
.Sh RETURN VALUES
If the tree was traversed successfully, the
.Fn ftw
and
.Fn nftw
functions return 0.
If the function pointed to by
.Fa fn
returns a non-zero value,
.Fn ftw
and
.Fn nftw
will stop processing the tree and return the value from
.Fa fn .
Both functions return \-1 if an error is detected.
.Sh ERRORS
The
.Fn ftw
and
.Fn nftw
functions may fail and set
.Va errno
for any of the errors specified for the library functions
.Xr close 2 ,
.Xr open 2 ,
.Xr stat 2 ,
.Xr malloc 3 ,
.Xr opendir 3
and
.Xr readdir 3 .
If the
.Dv FTW_CHDIR
flag is set, the
.Fn nftw
function may fail and set
.Va errno
for any of the errors specified for
.Xr chdir 2 .
In addition, either function may fail and set
.Va errno
as follows:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa depth
argument is less than 1 or greater than
.Dv OPEN_MAX .
.El
.Sh LEGACY ERRORS
The
.Fn ftw
and
.Fn nftw
functions are far more tolerant of symlink cycles and are lax in reporting
errors while accessing the initial path.  When
.Fn nftw
is passed
.Dv FTW_MOUNT ,
it will pass the mount point to the callback function.
.Sh SEE ALSO
.Xr chdir 2 ,
.Xr close 2 ,
.Xr open 2 ,
.Xr stat 2 ,
.Xr fts 3 ,
.Xr malloc 3 ,
.Xr opendir 3 ,
.Xr readdir 3 ,
.Xr compat 5
.Sh STANDARDS
The
.Fn ftw
and
.Fn nftw
functions conform to
.St -p1003.1-2001 and
.St -susv3 .
.Sh HISTORY
Prior to MacOS X 10.4 
.Nm ftw
did not follow symlinks.
.Sh BUGS
The
.Fa depth
argument is currently ignored.
